On Tue, Jan 18, 2022 at 4:32 PM Andres Freund <and...@anarazel.de> wrote: > I wonder if a very different approach could make sense here. Presumably this > wouldn't need to be queried at a very high frequency, right? If so, what about > storing the latest commit LSN for each backend in PGPROC? That could be > maintained without a lock/atomics, and should be just about free. > pg_last_committed_xact() then would have to iterate over all PGPROCs to > complete the LSN, but that's not too bad for an operation like that. We'd also > need to maintain a value for all disconnected backends, but that's also not a > hot > path.
One other question on this: if we went with this would you expect a new function to parallel pg_last_committed_xact()? Or allow the xid and lsn in the return of pg_last_committed_xact() potentially not to match (of course xid might also not be present if track_commit_timestamps isn't on)? Or would you expect the current xid and timestamp use the new infrastructure also? Thanks, James Coleman
